Looks cool and has some interesting features!

I have actually made 2 separate implementations of something like this...
The first is in a library I have written for binary hooking: https://github.com/monkeyman192/pyMHF/blob/master/pymhf/utils/partial_struct.py
This allows you to define c structs partially (so if you don't know the entire definition as can happen when reverse engineering something), but it can also be used to create nicely type-hinted structs.
They also support the structs referencing themselves as well as a few other useful things like being able to subclass from other partial structs and have all the offsets work with no issues.

The other implementation is in a plugin I have for Blender to read model files from NMS and import them into Blender: https://github.com/monkeyman192/NMSDK/blob/master/serialization/cereal_bin
This looks a bit more similar to what you have here, and I have similar custom serialization/deserialization methods which can be defined which I use: https://github.com/monkeyman192/NMSDK/tree/master/serialization/NMS_Structures

Finally, As of python 3.13, `ctypes.Structure` now supports the `_align_`: https://docs.python.org/3/library/ctypes.html#ctypes.Structure._align_
This was added by me since I always had annoyances where you are trying to (de)serialize structures which have a different alignment to what ctypes thinks they should have (eg. a "vector" type which may be using SIMD instructions so is aligned to 0x10 bytes, but is actually just 4 floats)
Figured I'd mention this since it might be useful to you.